While driving at freeway speed I felt a rapid vibration start in my rear end. I pulled over and the right rear wheel had a burning oil smell coming from it. I got back on the road and it was gone. This has happened 3 times over the last month or two.

I would check that, it could be many different things, better get that on a lift or jack stands and see whats going before it costs you way more. Just so you know , ANY vibration is VERY bad, it means something is WAY out of spec and most specs are .000 tolerances so when you CAN FEEL it, it's costing you more

this is true, my rear dana44 was vibrating so bad after i started getting into the axle it was so bad i just replaced the whole thing